September 2005Pacific Creek Separo SE300I
Integrated Power Amplifier
An Appealing Approach, But Can It Deliver The Goods?Review By Dick OlsherClick here to e-mail reviewer

Pacific Creek — the company — is the new kid on
the block, in business only since October 2003. You cannot say that, however,
about its founder and chief designer, Jerry Wang. He has been actively building
tube amplifiers for over 30 years, having built his first tube project when he
was only 13 years old. With a technical background in radio circuit and system
design, and digital signal processing, the transition to high-end audio combines
Jerry's engineering skills with his passion for tube sound. The Separo SE300I
represents Pacific Creek's inaugural product, a 10 watt per channel integrated
stereo amplifier — a single-ended triode design featuring the ever-popular
300B power triode. The gold-anodized front panel and elegance of finish in
general suggest a lofty retail price. Its actual retail price ($1899) should
turn more than a few heads, and is only possible because the Separo, while
designed in the US, is being manufactured in China.

The TechnologyThe power switch, volume pot, and an input selector that controls four
line-level inputs adorn the front panel. In line with other classic 300B
designs, the philosophy here is simpler is better. There are only three active
stages. After negotiating the input selector and volume pot, the signal arrives
at a 12AU7 based Series Regulated Push-Pull (SRPP) input stage. The SRPP,
also known as a Mu Follower, has proven to be an extremely popular circuit over
the past 15 years, and for good reasons, as it offers substantial gain with low
output impedance. The SRPP feeds the driver stage, a triode-connected 6L6. This
choice was based on the desire for a low-gain stage with a large peak-to-peak
voltage swing. Actually, instead of a New Old Stock (NOS) 6L6, the Separo uses a
Russian 6P3 (6L6 equivalent).

The output stage consists of a Chinese 300B-98, self-biased for long-term
stability. The output transformers are said to be oversized and capable of
handling nearly 20 watts in single-ended operation. The primary's impedance is
3,500 Ohm, which is on the high side of the optimal load for a 300B, but was
chosen to provide a damping factor of about 6. Secondary winding taps are
provided for 4 and 8 Ohm loads. No global or local negative feedback is used.
The power supply is vintage-tube in conception with a modern touch thrown in:
tube rectification using a 5Z3P (a Chinese 5U4G equivalent), a choke input
filter, and a DC supply for the 300B filaments.

The SoundRight out of the box, the SE300I required a long break-in period - emphasis
on long. Initially, harmonic textures sounded dry and grainy to the extent that
would have required chaining me down to my listening seat in order to continue
serious listening. A 300B SET amplifier's calling card is typically a sweet and
mellow harmonic spectrum, rich in consonant second order distortion products —
a high-fat Atkins Diet, if you will, for your matching speakers. Being so far
off target was definitely worrisome. Fortunately, after days of break in, the
gap narrowed between expectation and reality, but not sufficiently to satisfy my
musical palette. The next step in the process was tube rolling, the time-honored
practice of spicing up the sound using tube substitutions.

I did experiment with substitutions for the Chinese 12AU7 and 300B output
tubes, but I did not touch the Russian 6P3. The most transforming tube roll-in
turned out to be the KR Audio 300B Balloon. Image focus and stage depth
perspective improved, textures became sweeter and more luxurious — just what a
old tube romantic needed! The moral of the story is that the Chinese 300B-98
does not appear to work well in this context. And there is no reason for
prospective customers to be forced to purchase this tube. A more
customer-friendly policy would be to provide for either 300B alternatives or
optionally sell the amplifier without output tubes.

It was now time to take stock of the situation. The soundstage was reasonably
well reproduced, with convincing width and depth, but lacked adequate projection
into the room. Image focus was very sensitive to absolute signal polarity. With
the "correct" polarity setting, however, instrumental outlines snapped into
focus resulting in good spatial resolution. Bass lines were not reproduced with
the tightness and control of solid-state amplification, but certainly the Separo
was no better or worse in this regard than many other SET amplifiers. Treble
extension was very credible for a SET design. I am certainly not a fan of an
overly liquid and dark presentation, which is symptomatic of a severely
restricted power bandwidth. The Separo managed to project a "sunny" disposition
with good treble detail. For example, Ernestine Anderson's rendition of "What a
Diff'rence a Day Made" [Never Make Your Move Too Soon Concord Jazz
CJ-147] came through with crystalline enunciation. However, the tonal balance
was not entirely to my liking, being a bit recessed in the midrange.

So far pretty good. But storm clouds were gathering on the horizon. It has
been said that a life is not measured by the number of breaths you take but
rather by the number of moments that cause you to hold your breath. It became
clear that with the SE300I in the chain, those moments were precious few; the
music's tension and drama were being substantially siphoned off. Imagine a taut
balloon that is suddenly pricked by a pin. The explosive pop and subsequent
startle reaction are due to the sudden release of pressure. It was as though the
Separo was allowing the air to leak slowly out of the balloon. Hair-raising
performances were turned pretty mundane. A couple of examples are in order. A
young Joan Baez gives a deeply haunting performance of "House of the Rising Sun"
[Joan Baez Vanguard VSD-2077], a ballad of a girl gone wrong. Instead of
being riveted to my seat, I was fiddling with the volume control trying to coax
more drama out of the music. The lack of dynamic scale was also painfully
apparent during Walton's Belshazzar's Feast [EMI AN-324]. André
Previn whips up the massive forces of the London Symphony orchestra and chorus
to imposing levels of dramatic intensity. The Separo simply failed to negotiate
the transition from loud to very loud. It could not shift gears fast enough to
keep up with the action. There are imperfections I can forgive in reproduced
music, but this is not one of them. Take away the emotional underpinning of the
music, and what's left of reproduced music is nothing but a canned, uninspiring
copy of the real thing.

ConclusionDespite its good intentions, I found the sound of the Separo SE300I to be
ultimately disappointing. This is all the more frustrating in view of the design
effort and parts quality inherent to this product. Matched with a premium pair
of 300B tubes, such as the KR Audio Balloon, soundstage dimensions, image
outlines and harmonic textures are certainly competitive with the performance
benchmark set by similarly priced 300B based SET amplifiers. However, its
Achilles heel is lack of dynamic conviction. Dramatic tension is the life force
that energizes reproduced music. It starts with the reproduction of dynamic
nuances, the subtle details that help convey urgency and emotion, and finishes
with the uncompressed ascent of loud passages. In the case of the SE300I, its
performance in these areas is on "life-support." For the record, I do find the
Separo's design approach appealing and I hope that Pacific Creek manages to
implement the requisite modifications to resolve what I consider to be an
obvious and critical sonic problem.

Tonality

Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High-frequencies (3,000Hz on up)

Attack

Decay

Inner Resolution

Soundscape width front

Soundscape width rear

Soundscape depth
behind speakers

Soundscape extension into the room

Imaging

Fit and Finish

Self Noise

Value for the Money

Manufacturer's ReplyIt was a shock and disbelief when we first saw Dick Olsher's review, as we received nothing but praises from existing customers so far. We raced to do a thorough check of the returned sample as soon as we received it, but could not find anything wrong with it. We could not help thinking, what's wrong with Dick?

The mystery began to unfold one day, when we tried to burn in an
E34I (our entry level EL34 amp) and did a quick side by side comparison to the returned sample. The humble E34I clearly outperformed the returned
SE300I sample. This kept us busy for a while and we finally realized that the sample we sent to Dick had excessive bias which in turn caused core saturation in the output transformers. The
"thorough" test (we thought it was) simply could not catch the failure that Dick was able to detect with his ears.

We are sending a replacement unit to Dick and hope he has time for a follow up review. Needless to say we are also adding steps to prevent the same failure from happening in the field again.